Nonchromate metallic surface treating agent for PCM use, method for PCM surface treatment, and treated PCM steel panel

Abstract

A nonchromate metallic surface treating agent comprising (a) a silane coupling agent and/or a hydrolytic condensation product thereof, (b) water-dispersible silica, and (c) a zirconium compound and/or a titanium compound is disclosed. The present invention also discloses a method for treating a surface of a PCM steel panel, a method of producing a PCM steel panel, and a PCM steel panel as produced by the method.

What is claimed is:  
     
       1. A non-chromate metallic surface treating agent for precoated metal which comprises, in each liter thereof, 
       (a) a silane coupling agent and/or a hydrolytic condensation product thereof in an amount of 0.01 to 100 g/l,  
       (b) water-dispersible silica in an amount of 0.05 to 100 g/l (solids), and  
       (c) a zirconium compound in an amount of 0.01 to 50 g/l in terms of zirconium ion and/or a titanium compound in an amount of 0.01 to 50 g/l in terms of titanium ion.  
     
     
       2. The non-chromate metallic surface treating agent for precoated metal according to  claim 1  containing one or more members selected from the group consisting of sulfide ion, thiosulfate ion, persulfate ion and a triazinethiol compound, in an amount of 0.01 to 100 g/l. 
     
     
       3. A method of treating a metallic surface which comprises treating a metal-coated steel panel with the metallic surface treating agent according to  claim 1 . 
     
     
       4. The method of treating a metallic surface according to  claim 3  wherein the metal-coated steel panel is a zinc-coated steel panel. 
     
     
       5. A method of producing a precoated metal steel panel which comprises treating a surface of a metal-coated steel panel with the metallic surface treating agent according to  claim 1  and applying a chromium-free primer and a top coating serially thereon. 
     
     
       6. A precoated metal steel panel which is obtained by the method according to  claim 5 . 
     
     
       7. A method of treating a metallic surface which comprises treating a metal-coated steel panel with the metallic surface treating agent according to  claim 2 . 
     
     
       8. The method of treating a metallic surface according to  claim 7  wherein the metal-coated steel panel is a zinc-coated steel panel. 
     
     
       9. A method of producing a precoated metal steel panel which comprises treating a surface of a metal-coated steel panel with the metallic surface treating agent according to  claim 2  and applying a chromium-free primer and a top coating serially thereon. 
     
     
       10. A precoated metal steel panel which is obtained by the method according to  claim 9 .